First measurements of thermospheric winds in Antarctica by an optical ground-based method

The installation of a Fabry–Perot interferometer at Halley (75.5° S, 26.8° W; L = 4.2), Antarctica, has now allowed the first comparison to be made between Southern Hemisphere ground-based thermospheric wind measurements and the predictions of a three-dimensional time-dependent thermospheric global circulation model. Because some terms of the thermospheric momentum equation are more dependent on geomagnetic than geographic latitude, the large separation of these that exists at Halley provides a distinct contrast to the dynamic behaviour observed in the more frequently studied northern polar thermosphere. Although the initial results from the experiment are in general agreement with the model, some consistent and significant differences between the observed wind field and that predicted are evident in the morning sector. These may be related to uncertainties in mapping magnetospheric boundaries to ionospheric heights in the Southern Hemisphere.